1. Field of the Invention
The present invention relates to traveling vehicles such as an overhead traveling vehicle (OHT), an automated guided vehicle (AGV), a rail guided vehicle (RGV), or the like. In particular, the present invention relates to a technique of implementing control in a diverging section or a merging section of such a traveling vehicle.
2. Description of the Related Art
In a technique disclosed in JP2005-284779A, a collision prevention sensor is provided in a traveling vehicle such as an overhead traveling vehicle to monitor a leading traveling vehicle for preventing interference with the leading traveling vehicle. Further, a ground controller restricts entry of the traveling vehicle into a diverging section and a merging section to ensure that only one traveling vehicle can enter the diverging section or the merging section. Hereinafter, control where the ground controller's permission is required for the traveling vehicle to enter a certain area, and the number of traveling vehicles that can be present in the certain area is limited to one or less is referred to as the blocking control. Further, an area where entry of the traveling vehicle is restricted by blocking control is referred to as the blocking area.
In general, the conventional blocking area is several times longer than the vehicle length of one traveling vehicle for the following reasons. For example, in the case of the diverging section, it is difficult to detect a traveling vehicle diverging from the diverging section by a collision prevention sensor from a position upstream of the diverging section. Further, it is difficult for a traveling vehicle in a curve segment at the exit of the diverging section to monitor traveling vehicles in a straight segment downstream of the diverging section by the collision prevention sensor. Likewise, in the case of the merging section, it is difficult for a traveling vehicle curving at an entrance of the merging section for entering the merging section, to detect traveling vehicles in the merging section using the collision prevention sensor. Therefore, a region upstream of the merging section is also included in the blocking area. Further, it is difficult for a traveling vehicle curving in the merging section to detect traveling vehicles at the exit of the merging section by the collision prevention sensor. Therefore, a region at the merging section is included in the blocking area as well. Under the circumstances, the blocking area becomes large. Since the number of traveling vehicles that can pass through the blocking area per unit time is substantially inversely proportional to the size of the blocking area, the efficiency of the traveling vehicle system is low.